A people mover that can reach 1,200kmh?
IN THE sparse desert north of Las Vegas, a car-sized sled rocketed to more than 160kmh in just 1.1 seconds.
There is no fuel or powerful engines at play.
The sled was propelled by electromagnets.
What unfolded before a crowd of 300 last Wednesday is the first successful test of a futuristic mode of transport called the hyperloop.
It was an idea planted by Elon Musk, chief executive of electric-car company Tesla Motors, back in 2013.
Then, the founder of rocket-maker SpaceX outlined a vision of pods in giant vacuum tubes that could take passengers from Los Angeles to San Francisco in about 30 minutes.
The concept thrilled some but was met with scepticism by others.
At that time, Wired Magazine described the hyperloop as "a totally imaginary transportation device" that would perhaps look like "green tubes on Futurama".
But the demonstration by Hyperloop One showed that this seemingly implausible idea may soon be brought to life.
The Los Angeles company is among several others vying to develop the technology.
Its co-founder, Brogan BamBrogan, reportedly hailed the test as a major milestone.
During the test, the sled was set on a train track before it shot to 160kmh by electromagnets while electricity was shot into copper coils.
If the development goes smoothly, the sleds will levitate and carry pods in a test later this year.
Hyperloop One's chief executive, Rob Lloyd, predicted a hyperloop system would transport cargo by 2019 and people by 2021, reported Reuters.
Given that the pods may travel at speeds approaching 1,200kmh, the question is whether humans can tolerate riding the system without feeling sick.
The projected speed is just shy of breaking the sound barrier, which is 1,235kmh.
That said, the acceleration is the factor that would cause nausea, not the extreme speed, said an article by Scientific American magazine last week.
Such gravitational forces, or G-forces, are also felt when a plane takes off.
Once the jet reaches a cruising speed, people on board are back to feeling normal.
While a hyperloop can mimic that to minimise riders' discomfort, problems arise when the pod makes a turn.
"Anybody who's turned a car on a sharp turn knows that you're pulled sideways in your seat by the centrifugal forces," Nasa Ames research psychologist Lee Stone was quoted by Scientific American as saying.
Similarly, Christopher Merian, chief engineer of Massachusetts Institute of Technology's effort to build a hyperloop, told the BBC that the key problem is that it cannot handle corners.
To travel in an almost straight line from A to B could mean cutting through historic sites and private property.
Lisa Marie Alley, a spokesman for California High Speed Rail Authority, said a hyperloop may also run into challenges such as right of way, environmental permits and approvals.
Still, the start-ups are forging ahead - and even rail companies are betting on them.
French national rail company SNCF has recently joined a group of backers for Hyperloop One that has raised US$80 million (S$110.3 million) so far.
WHAT IS HYPERLOOP?
A CONCEPTUAL transport system where people whiz around in pods propelled through vacuum tubes at more than 1,000kmh.
The pods would ride on an air cushion - and so would appear to be "levitating".
One way to power the hyperloop is electromagnetic suspension. Removing the air from the tubes would also reduce air resistance - which has hindered current high-speed rail systems.
This could make journeys shorter yet require less energy than conventional trains.